Condensing boilers are described in EP-A-0789203. This publication describes a gas fired condensing boiler. These boilers are called condensing boilers because the gases produced by combustion are cooled inside the apparatus until the water vapor contained therein condenses, so as to recover the latent condensation heat and transfer it to the water to be heated, which flows through said boilers. This latent heat is sometimes also used to pre-heat the combustion air. A problem associated with these condensing boilers is that the liquid condensate by-products of the combustion must be contained and channeled away for disposal. Furthermore, heat exchanger materials must be capable of withstanding the corrosive liquid condensate by-products. Steps should also be taken to ensure that the burner and igniter systems, along with other system elements such as sensors, are not fouled by moisture or condensation.
Normally, condensing boilers use natural gas as fuel. For example in The Netherlands, which is equipped with a wide spread natural gas grid, many households use a condensing boiler for domestic heating in combination with warm water supply. The wide application of these condensing boilers is due to the attractive energy efficiency of these apparatuses and the presence of the natural gas supply grid.
A disadvantage of these apparatuses is that they cannot be easily applied in regions where no natural gas grid is present. A solution to this problem is to use a liquid fuel. Liquid fuels can be easily transported to and stored by the end user. A disadvantage of the use of liquid fuels is however that the condensing boiler and/or the associated chimneys have to be made from different, more corrosion resistant, materials. For example EP-A-699872 describes a condensing boiler wherein use is made of carbon materials to avoid corrosion. DE-A-3434415 describes another heating device wherein flue gasses are cooled against combustion air in a heat exchanger made of corrosive resistant material. DE-A-3238762 is another example of a heating device wherein a corrosive resistant material is used for this purpose. These solutions are a disadvantage for the manufacturer of condensing boilers because it would result in two types of boiler apparatuses, namely one operating on gas and one operating on liquid fuel. Moreover the apparatus using a liquid fuel would be more expensive due to the different more corrosive-resistant material required.
It would be useful to provide a process for operating a condensing boiler for regions not equipped with a natural gas supply grid.